Conventional fuel delivery systems for automotive vehicles typically include a fuel tank pressure transducer (FTPT), mounted near a fuel tank, to estimate the vapor pressure within the fuel tank. This vapor pressure estimate is relayed to an electronic engine controller so that the controller can adjust engine operation based on the estimated vapor pressure and/or determine whether a leak has occurred in the fuel tank based on the estimate vapor pressure. In another example, the controller may use the estimated vapor pressure to manage fuel tank pressure, as well as determine when the fuel tank may be purged. Purged vapors from the fuel tank are then vented to the intake manifold of the engine to be consumed therein. Alternatively, the vented vapors may be stored in a carbon canister coupled to the fuel tank. The canister may be part of an evaporative emissions system.
In one example, the FTPT may be positioned on the vapor side (i.e., downstream) of the fuel tank for the purpose of performing a leak diagnostic and vapor detection in the evaporative emissions system. However, the inventors herein have recognized problems with positioning the FTPT external to the fuel tank and downstream of the fuel tank in the evaporative emissions and fuel system. As one example, this positing of the FTPT may result in increased noise of the FTPT output signal. Specifically, as the liquid fuel inside the fuel tank cools and heats up, it becomes the driving function for pressure and vacuum buildup inside the fuel tank. However, the downstream positioning of the FTPT may result in a degraded signal to noise ratio, thereby resulting in a distorted pressure reading and less accurate estimate of the pressure and vacuum buildup due to fuel tank thermal gradients.
As another example, the remote location of the FTPT outside of the fuel tank can lead to exposure of the sensor to external conditions such as dirt or underbody rust. An inline FTPT positioned downstream of the fuel tank (e.g., such as in a vapor tube downstream of the fuel tank) may use extra transducer packing measures to reduce exposure to external conditions. Further, issues may arise when vapor permeates through the connection joints leading to the FTPT in the vapor tube.
Finally, positioning the FTPT outside of the fuel tank may result in reduced efficiency and speed of the sensor response time (e.g., via a transport delay) as vapor pressure changes occur within the fuel tank. However, faster response times may be desired for detecting certain pressure conditions within the fuel tank and taking corrective action based on the detected pressure conditions. For example, in a non-integrated refueling canister only system (NIRCOS), a fuel tank may be depressurized prior to a refueling event. If changes in vapor pressure are not accurately measured with reduced time delay, a fuel door may be opened before the fuel tank pressure has reached a lower threshold level.
Other attempts to address these issues include combining the FTPT with a fuel level indicator located inside of the tank. One example is shown by Gary Lee Casey et. al. US 2007,0272,025. Therein, a fuel tank module control system is configured to measure fuel level and fuel tank vapor pressure through a single sensor.
However, the inventors herein have recognized potential issues with such systems. As one example, a disadvantage of such sensor lies in its dependency on the output of a single sensor within the apparatus. To obtain the fuel level and fuel tank pressure, the sensor alternately measures the pressure of the pressurized vapor as well as the pressure of a fuel column. In the event of a mechanical error (e.g., a sensor malfunction or degradation), both the fuel pressure and fuel level output would be lost and unavailable for adjusting engine operation.
In one example, the issues described above may be addressed by a system for a fuel tank comprising a level sensor positioned inside the fuel tank and including a float arm and a floating body coupled to a first end of the float arm. The system further comprises a pressure sensor integrated with the floating body. As described herein, integrated may refer to the pressure sensor being directly and physically coupled with at least a portion of the level sensor. In this way, both the level and pressure sensors are integrated into one unit within the fuel tank. As a result, response times (due to transport delays) of the pressure sensor may be reduced and the resulting pressure signal may have less noise. Additionally, the packaging space of the two sensors within the fuel tank may be reduced.
As one example, a pivotable float arm of the fuel level sensor utilizes the buoyancy of a floating body to measure the fuel level while an integrated gauge pressor sensor (e.g., FTPT) simultaneously obtains a direct pressure measurement of the vapor pressure within the fuel tank. In one example, the pressure sensor may be positioned at a top surface of the float with an atmospheric reference port of the sensor positioned underneath the sensing port (e.g., portion) of the pressure sensor. Further, an electrical connection of the pressure sensor may be routed through an interior of the float arm. As a result, the pressure sensor electrical connections may be isolated from the fluid within the tank. Additionally, the electrical connections of both the level sensor and pressure sensor may be electrically connected to a common control unit of a fuel delivery module within the fuel tank. This may reduce electrical connections within the tank and provide for a common electrical connection outlet from the fuel delivery module and to the engine controller.
The positioning of the pressure sensor within the fuel tank and on a floating body of the level sensor results in a pressure sensor output with reduced noise and faster response time (due to reduced transport delay). Additionally, the exposure to external conditions that may result in sensor degradation may be reduced since the pressure sensor is positioned within the sealed fuel tank. Further, integration of the pressure sensor within the fuel level sensor float simplifies packaging.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.